干旱区生态环境知识资源中心

In order to elucidate the mechanism of the purification system in the Yatsu tideland, we have analyzed sediments of the Yatsu tideland and the Shibaura canal by instrumental neutron activation analysis (INAA) and (57)Fe Mossbauer spectroscopy. In addition, we have examined the distribution and behavior of Fe in pore water by several analytical methods, such as ICP-AES, capillary electrophoresis (CE) and Absorption Spectrophotometry. We defined a purification system in which metals are fixed as stable forms, like sulfide into the sediments. The vertical distribution of Fe in pore water observed by ICP-AES showed a feature complementary to that of pyrite in all core samples. This suggests that Fe dissolved into pore water from the sediments was consumed for pyrite formation. The same concentration to the prepared solution was observed for Fe(2+), while the concentration of Fe(3+) was detected only at 1 similar to 4% of that for the prepared solution by CE. We thus concluded that Fe(3+) is the dominant species in pore water. Moreover, Fe(3+) makes a variety of chelate complexes with something that is assumed to be organic matter. Normally, Fe(3+) could be soluble in pore water by combining with chelating agents, and solved Fe(3+) should be consumed to form pyrite. Therefore, we could explain why the Yatsu tideland shows a "high potential of purification system". Furthermore, our results imply that the Fe chelate complexes in the Yatsu tideland could be a source of Fe supply to the ocean, and help to solve the sea desert problem. On the whole, pore water plays not only a key part in a purification system, but also an important part in the ocean.